1. Field of the Invention
The invention relates to the field of flow indicators and in particular to a flow indicator used in drip irrigation systems, which flow indicator is capable of providing a visual indication of high, normal and low flow rates, which flow indicator is field adjustable, and which flow indicator uses a magnetic transmitting means to transmit a signal indicative of flow to a visual indicator.
2. Description of the Prior Art
It is necessary to know the flow rate in a drip irrigation system since large acreages may be drip irrigated with thousand of yards or even miles of lines. Even with the best of filtering precautions, some water borne debris will be inserted from the water source into the lines, which will tend to accumulate at the distal ends of the submains. Back suction will tend to also draw dirt and debris from the emitters into the lines or to clog the emitters every time the system is turned off. In some applications lime deposits can build up over time just as in building water distribution plumbing. As the flow rate slowly decreases a portion of the crop will become underwatered resulting in lowered production and even possible crop loss through dehydration or disease.
In drip irrigation systems the lines are very light gauge and can be easily torn or cut with even a dull edge. Contact with agricultural equipment or tools can easily sever a line without this fact being immediately noticed. Drip lines are also susceptible to damage by animals, such as coyotes, gophers and other rodents, which will chew the lines in mistaken identification of food. Therefore, emitters or small lines can easily open up and be unnoticed if the flow rate is not scrupulously watched. A portion of the crop will be over watered not only resulting in wasted expensive water, but in loss of fruit or root production through the production of excess vegetative growth or crop loss through disease.
As a result flow rate in extensive commercial drip irrigation systems is carefully monitored, as often as not by expensive remotely telemetered electronic flow meters. While the use of such meters may be economically feasible for the mains, the flow rate in the submains and smaller lines must also be monitored since damage typically occurs locally and the flow in every locality must be known.
Moore, "Flow Indicator," U.S. Pat. No. 3,857,277 (1974) is directed to a flow indicator as shown in FIGS. 1-3 of that reference. The flow indicator 10 comprises a housing 12 which has a chamber 14 therein and includes an inlet opening 16 and an outlet opening 18 which respectively communicate with opposite ends of the chamber. A flexible flap 20 hingedly supported on the housing within the chamber 14 is disposed in the path of fluid flow from the inlet opening 16 to the outlet opening 18 for flexure about generally parallel axes and generally toward the outlet opening in response to fluid flow through the housing. A permanent magnet 22 carried by the flap 20 actuates at least one magnetically responsive switch 24 supported by the housing and adapted for connection in an external electrical circuit to operate an indicator or alarm or to operate relays or the like to provide automatic system control. The switch 24 is within the magnetic influence of the magnet 20 during at least a portion of flexure movement of the flap 20 toward the outlet opening 18. The housing 12 is provided with a transparent observation port through which the relative position of the flap 20 may be viewed.
Anderson et,.al., "Fiberoptic Flow Indicator System," U.S. Pat. No. 4,596,442 (1986) is directed to a fiber optic flow indicator system having a first magnetic member 14 comprises an elongate member 54, a magnet 56, and a paddle 58. First magnetic member 14 is pivotally mounted about point 60 to body member 12. Elongate member 54 extends from pivot 60 downward and beyond end 64 of body member 12. A spring 66 extends from sleeve 62 downwardly to stop 68 about the outer surface of elongate member 54. Spring 66 causes the elongate member 54 to return to an original position. Second magnetic member 16 comprises a magnet 72, a casing 74, an arm 76, and a reflective surface 78. Second magnetic member 16 is pivotally mounted to slotted member 46 about point 80. Second magnetic member 16 is pivotally mounted so as to allow the free rotation of the second magnetic member about pivot point 80. In operation, the reflective surface 78 will move in relation to the existence or absence of fluid flow acting on paddle 58. Since magnets 56 and 72 have their north poles adjacent each other, these magnets act to repel each other.
Muhleisen, "Flow Indicator", U.S. Pat. No. 2,029,633 (1936) is directed to a flow indicator having a generally rectangular clapper 14 of magnetized material disposed in the fluidway 13 and pivoted by means of a detachable pin 15 from the lugs 9 or 10, according to the direction of flow. Door 16 is made of diamagnetic opaque material, and it closes the lateral opening provided in the casing, thus completely enclosing the fluidway against possible leakage. In the space between the door and glass 16a, is an indicator 19 of magnetic material. The indicator is pivotally supported by a pin 20, aligned with the pin 15, and projecting from the door 16. The indicator is counterbalanced by a weight 23 applied to the arm 21. The indicator confronts the edge of the clapper 14 and is substantially equal in length with that edge. In use, the clapper 14 is turned and positioned by the flow of liquid through the casing and since it and the indicator are of magnetic material, and since one of them, the clapper in the present instance, is magnetized, the indicator follows the movement of the clapper and shows the condition of flow of the liquid.
Klos et.al, "Fluid Flow Sensor with Flexible Vane," U.S. Pat. No. 4,931,776 (1990) is directed to a fluid flow sensor with flexible vane as shown in FIG. 1 within the cavity 16. A vane assembly 22 of thin welded metal is attached to the housing 10 with screws 24 and nuts 26. A first electrical connection tab 28 is attached to one of the screws 24 on the outside of the housing 1 0 to provide an electrical connection point to the vane assembly 22. A second electrical connection tab 32 is held on with the set screw 30 with a nut 34. In operation, the sensor is connected serially in a fluid flow line. As the flow rate through the sensor is increased from zero, at some first limit point, called the flow rate at closing, it becomes sufficient to elastically bend vane 22 to contact set screw 30, so that an electrical connection path is made from the first tab 28 through screw 24, vane 22 and set screw 30 to second tab 32.
Karol et.al., "Flow Gauges," U.S. Pat. No. 3,224,270 (1965) is directed to flow gauges with a permanent magnet for signaling. A permanent magnet 22 is disposed within the passageway 13 and is adapted to be moved by the fluid when the latter is flowing through the conduit 12. In the presence of a fluid flow, the magnet 22 is moved in the direction of the outward taper of the conduit 12 to a position determined by a condition of equilibrium between the force of gravity and the force provided by the fluid flow. A plurality of magnetically operated read switches 28-42 are disposed sequentially along the outer wall 44 of the conduit 12, the switch 28 being adjacent the magnet 22 when the latter is in its rest position. As shown in FIG. 4, to overcome the force of gravity on the gate 71a, the gate is resiliently connected to a wall of the conduit 12a by springs 88 and 90, the latter being fixed to the opposite sides of the gate 71a and to the wall of the conduit 12a by any suitable means and may be counterbalanced dynamically, by any suitable means, as by counterweights which are not shown.
Large scale drip irrigation systems, such as used for drip irrigation of timber grown for paper pulp production, typically employs drip irrigation lines extending up to 660 feet or more arranged in networks covering tens to hundreds of acres. These lines must be inspected and maintained to determine both whether the drip lines are clogged or breached. Therefore, some type of means must be provided to measure both high and flow rates indicating breached or clogged drip lines. Further, the indicator must be simple, rugged, reliable, inexpensive to manufacture, easy to maintain, and easily visually inspected. The indicator must provide some type of visual indication in the field of either high or low flow rates. Ideally, the flow indication must be such that a worker can check the indicator quickly and unambiguously as he passes by on a motorized vehicle. Thus, the indicator must be of such a nature that if unambiguous visual indication of high, normal or low flow rates can be made on site within seconds or less.
What is needed is a flow meter that can be adjusted in the field to compensate for normal point-to-point system variations, is simple, rugged, inexpensive, reliable, and capable of given a quick, easily observable indication in the field of high, normal or low flows with the range of flow rates and pressures typically used in drip irrigation systems.